FirstUniqueChar

char unique (String str) {
    HashMap<Character, Integer> map = new HashMap<Character, Integer>();
    Set<Character> set = new SortedHashSet<Character>();
    
    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (map.containsKey(c)) {
           map.put(c, map.get(c) + 1);
           set.remove(c);
        } else {
           map.put(c, 1);
           set.add(c);
        }
    }
   
    if (set.size() == 0) {
        throw new NoUniqueCharException();
    } else {
        for (Character c: set) {
            return c;
        }
    }
}


char unique2 (String str) {
    LinkedHashMap<Character, Integer> map = new LinkedHashMap<Character, Integer>();
    
    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (map.containsKey(c)) {
           map.put(c, map.get(c) + 1);
        } else {
           map.put(c, 1);
        }
    }
   
    for (Map.Entry<Character, Integer> e: map.entrySet()) {
        if (e.getValue() == 1) {
            return e.getKey();
        }
    }
    
    throw new NoUniqueCharException();
}